Vacuum furnace



H. R. PALMER VACUUM FURNACE Jan. 8, 1963 2 Sheets-Sheet 1 Filed June 19,1961 INVENTOR. Howard R. Palmer Jan. 8, 1963 H. R. PALMER VACUUM FURNACE2 Sheets-Sheet 2 Filed June 19, 1961 INVENTOR. Howard R. Palmer UnitedStates Patent ()fliice Patented Jan. 8, 1963 3,072,392 VACUUM FURNACEHoward R. Palmer, Henderson, Nev., asslgnor to Titanium MetalsCorporation of America, New York, N.Y., a corporation of Delaware FiledJune 19, 1961, Ser. No. 118,039 Claims. (Cl. 263--3) This inventionrelates to a furnace and more particularly to a furnace for heatingmetallic strip in vacuo.

Metallic strip is generally produced in the form of a coil forconvenience in handling during processing, and later transportation andsale. Such a coil may consist of a long length of strip and becorrespondingly heavy and bulky. Heating such as coil is a longprocedure since heat transfer to the central portion is extremely slow.Therefore such strip is often heated by unwinding a coil, heating thestrip progressively as it is unwound and then rewinding it into anothercoil. Conditions often require this operation to be conducted in vacuo,for example, when heating titanium, zirconium or other reactive metals,and also certain steels. The design and construction of a furnace" forheating coiled strip in vacuo has heretofore. been diflicult toaccomplish since mechanical problems of handling the heavy coils, ofkeeping the structure vacuum tight and applying suitable heat toprovidethe proper heat treatment, are diflicult to solve.

:A principal object of this invention is to provide an improved furnacefor heating metal strip in vacuo. An-

' other object of this invention is to provide a furnace for heatingmetal strip in vacuo which is simple and convenient to load and unloadwith heavy coils of metal strip. Another object of this invention is toprovide a furnace which is readily loaded and unloaded and which iscapable of being evacuated to low pressure. These and other objects ofthis invention will be apparent from the following description thereofand from the annexed drawings in which:

FIG. 1 shows a vertical, longitudinal sectional view of a furnaceembodying features of this invention.

FIG. 2 shows a vertical cross-section of the furnace of FIG. 1 takenalong the line 2--2.

' FIG. 3 shows-'a vertical cross-section of the furnace of'FIG. 1 takenalong the line 33.

FIG. 4 shows a vertical cross-section of the furnace of FIG. 1 takenalong the line 44.

. FIG. 5 shows in some detail one of the heater elements as seen from 55in FIG. 1.

Referring now particularly to FIGS. 1 and 2, the fur- I nace comprises agenerally cylindrical, closed-end shell having a horizontal axis, thesaid shell 10 being divided or sectioned on a longitudinal planeextending axially and inclined upwardly and rearwardly at an anglebetween and 50 degrees to the vertical, and preferably about 30 degrees,to form a cover section 12 and a base section 14, which are hingedlyattached to each other at the juncture of their top edges as at 16. Thecomplete shell 10 may be suitably supported along its length by legs 18.

Horizontally and rotatably mounted in shell 10 and attached to the basesection 14 are spools 20a and 20b. These are mounted so that theirshafts projecting through thewall of base section 14 are sealed topreserve low pressure conditions inside shell 10. The details of thisconstruction will be described with particular reference to spool 20aand will be apparent from FIG. 2 in which spool 20a is fixedly attachedto a shaft 22 which is supported and journaled in a pair of spaced-apartbearings 24. These bearings 24 are in turn supported in place by tubmember 26 which transfixes the wall of base section 14 and is attachedand sealed thereto at its passage therethrough as by welding as at 28.Spool 20a is thus rotatably mounted in horizontal position and, bybearing tube 26, attached to base section 14. Flange 30 is attached andsealed, as by welding at 32 to the exteriorly projecting end of bearingtube 26.

Housing 34 is provided at one end with plate 36 through which theexterior end of shaft 22 passes with sufiicient clearance for rotation.At the other end of housing 34 is provided flange 38 which is attachedthereto as by welding at 40 and is of dimension to generally correspondwith bearing tube flange 30. Between flanges 38 and 30, and sealed toeach by provision of O-ring gaskets 42, is plate 44 through which passesshaft 22.

Rotating vacuum seal 46 is arranged to seal shaft 22 to plate 44 duringrotation thereof, being biased in sealing engagement by spring 48bearing against collar 50. Shaft 22 is connected by coupling 52 to shaft54 of electric fotor 56.

Spool 20a is arranged as the spool on which the strip is wound duringprocessing, while spool 2012, similar in mounting and shaft sealingdetails, is the spool holding the original coil and from which the stripis unwound.

Therefore a motor 56 is not always essential for powering of its shaft22 although it may be useful for back winding if necessary.

, Also rotatably mounted in horizontal positionin shell 10 and attachedto the base section 14 are a pair of lower cooling rolls 58. As will beseen more clearly in FIG( 3, each'of these is mounted on a shaft 60which is journaled at its inner end in bearing 62 which is supported byupright member 64 and brace member 66. Shaft 60 passes through plate 68which is attached at the inner end of tubular member 70 which piercesthe wall of base section 14 and whose projecting end carries outer shaftbearing 72. Passage of shaft 60 through plate 68 is sealed as in thecase of shaft 22 by provision of another rotating seal 46 biased by asimilar spring 48 bearing against collar 50. Shaft 60 is preferablyhollow as is also roller 58 to allow circulation therethrough of coolingfluid such' as water introduced by axial tube 74.

Also mounted in shell 10 on base section 14 are means for heating theunderside of a strip being treated in the furnace, and comprising anopen-top box-like heat shield 76 supported by uprights 78. Inside heatshield 76 are placed electric heater units 80 which are bent as shownmore clearly in FIG. 5. They are fabricated of high resistance alloy andare connected by lead wires 82 which pass through the wall of basesection 14 being insulated and sealed at such passage by bushings 84.

Also mounted in shell 10 and attached to the base section 14 isrotatably mounted guide roll 86. This guide roll is attached to ahorizontal shaft 88 which is journaled into bearings 90 which are inturn supported by pedestal 92.

Communicating with the interior of shell 10 is vacuum pipe 94 which isconnected through line valve 96 to vacuum pump 98. Motor 100 operatespump 98 through belt 102. Vacuum pipe 94 is provided with bleed line 104controlled by bleed valve 106.

The above describes elements which are attached to or associated withthe base section 14 of shell 10. The elements which are attached to orassociated with the cover section 12 of shell 10 will now be considered.

Upper cooling roll 108 is rotatably mounted inside shell 10 and attachedto cover section 12. It is mounted on shaft 110 which is supported atits inner end in bearin 11?. whi h is in turn supported by hangingbracket 114. Tubular element 116 transflxes the wall of cover section12, through which the outer end of shaft 110 passes and is provided withflange 118 to which is adjustably attached in sealing engagement bearingplate 120 and outer plate 122. Enclosed within housing 124, androtatably sealing shaft 110 to plate 122, is rotating seal 46, similarto those previously described biased by spring 48 against collar 59.Shaft 110 is hollow, communicating with the hollow interior of roll 1G8,cooling fluid, such as water, being supplied thereto through internalpipe 126. Cooling roll 108 is located so that it is laterally spacedmidway between lower cooling rolls 58 and arranged so that when coversection 12'is closed, its lower edge is somewhat lower than the upperedges of cooling rolls 58.

Means for heating the upper surface of a strip being treated are alsomounted in shell and attached to the cover section 12. An open bottomheat shield 128 is supported from cover section 12 by brackets 130.Inside heat shield 128 are placed electric heater elements 132' whichare bent to shape as shown. They are, like elements 80, fabricated ofhigh resistance alloy and are connected by lead wires 134 which passthrough the wall of cover section 12 being insulated and sealed at suchpassage by bushings 136.

The corresponding edges of cover section 1'2 and base section 14 ofshell 10 are provided with mating flanges 138 and 140 respectively. Oneof these, for example, flange 140'as shown is provided with a continuousgroove 142 which is fitted with continuous O-ring gasket 144 preferablyof rubber or other resilient material.

It is preferred as will be seen from the drawings that the tops of guideroll 86, the means for heating the under side of strip and lower coolingrolls 58 lie in the same general horizontal plane.

In operation, the cover section 12 of shell 16 is first.

raised as shown in FIG. 2; suitable mechanical hoisting means (notshown) may be employed if necessary. Then a coil of metal strip to beheat treated is placed on spool 21% and the free end of the strip 146 isunwound for a sufiicient length so that it may be laid on top of guideroll 86, then across the top of lower heat shield 76, then over the twocooling rolls 58 and finally temporarily attached to the surface ofspool 20a. Cover section 12 is then lowered so that cover section flange138 mates with base section flange 140, with gasket 144 compressed ingroove 142 to form a seal. lowers the top heat shield 128 onto thebottom heat shield 76 (suitable apertures being arranged in their endsto allow for passage therethrough of strip 146) and upper heatingelements 132 will be in position to heat the upper surface of strip 146,and bottom heating elements 80 will be in position to heat its underside. At the same time upper cooling roll 108 will be lowered intoposition to contact and depress sheet 146 thereby providing good contactarea for sheet 146 over the three cooling rolls. Bleed valve 106 isclosed and vacuum line valve 96 is opened and the interior of shell 10evacuated by operation of motor 100 actuating vacuum pump 98.

After suitably reduced pressure has been attained in shell 10, heatingelement connectors 82 and 134 are connected exteriorly of shell 10 to asuitable source of electric power (not shown). When these elements havereached the desired temperature motor 56 is operated to rotate spool20:: to rewind the coil onto this roll. It will be understood that therate of travel of the strip between the heating elements and thetemperature to which it is subjected during such passage will beadjusted to provide the desired heat treatment. Cooling rolls 108 and 58have been found effective to cool the heat treated strip so that it maybe recoiled without sticking or welding between turns. The heattreatment is continuously applied to the strip as the coil is unwoundfrom spool 20/) and rewound on spool 20a, with vacuum being maintainedinside shell 10. When the coil has been completely heat treated andrewound on spool 20 motor 56 is stopped, heater elements 132 and 80 aredisconnected or switched off and vacuum line valve 96 is closed. Thenbleed valve 106 is opened allowing the atmosphere to enter shell 10 andcover section 12 is raised. The heat treated and refound coil on spool25):: is then removed; if additional strip is to be procesed anothercoil may be placed on Closing of cover sect on 12 d spool 20b laidacross the heaters and coil and the heat treating operation repeated.

The furnace of this invention is particularly designed for vacuum heattreatment of metallic strip handled in the form of coils, and its uniquefeatures provide for proper maintenance of high vacuum, ease of loadingand unloading coils, and eificient and continuous progressive heattreatment. The angle of the juncture between the cover section 14 andthe base section 12 is important. This angle, between 20 and 50 degreesto the vertical, provides adequate horizontal opening for coils to beloaded onto spool 26b and unloaded from spool 20a. While loadingandunloading opening is adequate, at the same time the weight of thecover will provide good contact between it and gasket 144 so that whenthe vacuum pumping equipment is turned on suflicient initial seal willbe obtained so that reduced pressure inside shell 10 will tend to pullthe cover secton 12 and base section 14 together and thus perfect theseal. If the angle of the intersection of cover section 14 and basesection 12 is less than 20 degrees to the vertical, the free weightcomponent will generally be insufficient to initiate the seal. If theangle is greater than 50 degrees then, while efficient sealing can beobtained, the horizontal section of the opening is too much restrictedfor ready handling of the bulky and heavy coils in and out of thefurnace.

The location of the various elementsinside the furnace,

with respect to their attachment to the cover section 14- or' the basesection 12 is also important. With the upper cooling roll 58 and theupper part of the heating means attached to cover section 12 when thisis raised then both these elements are raised clear of the lower coolingrolls and the lower part of the heating means. This arrangement providesfor easy location of the strip end when it is originally placed instarting position spanning the furnace interior from spool 20]) to 20a.Metallic strip of the type readily handled by furnaces of the typedescribed is often stiff and difficult to handle if it has to bethreaded through a tortuous path. However, with the furnace of thisinvention, the starting end is s mply laid over the guide roll, thelower part of the heating means and the lower cooling rolls 58 towind-up roll 20a; When the strip end is in place lowering the coversection 14 automatically lowers the upper cooling roll 108 and heatshield 128 (with its heating elements) in their proper places on top ofthe strip.

The embodiment illustrated shows the furnace equipped with cooling rolls108' and 58 to cool the heated strip sufficiently so that it may readilybe coiled onto wind-up spool 200. In applications wherein the heatingtemperature is low, or where the characteristics of the metal beingtreated permit hot coiing, then, as will be apparent, the cooling rollsmay not be used. The advantages of the invention with respect to theease of loading and unloading, the initial sealing of the cover section14 to base section 12 and the benefits occuring from attachment of theupper heating means to cover section 14, will however, be obtained asotherwise.

The furnace of this invention is useful for annealing strip of reactivemetals such as titanium or zirconium and may also be employed for anneaing strip of other metals that may be affected by atmospheric exposureat annealing temperature.

I claim:

1. Apparatus for heating a metal strip in vacuo comprising; a generallycylindrical closed-end shell, having a horizontal axis and beingsectioned on a longitudinal plane extending axially and inclinedupwardly and rearwardly at an angle between 20 and 50 degrees to thevertical to form a cover section and a base section thereof, said coversection being hingedly attached to said base section at the juncture ofthe top edges of said base and cover sections, a pair of spaced apartspools horizontally and rotatably mounted in said she l and attached tothe base section thereof, means for rotating at least one of saidspools, a guide roll mounted in said shell and rotatably attached to thebase section thereof, means mounted in said shell and attached to thecover section thereof for heating the upper surface of a metal stripdisposed between and coiled on said spools, means mounted in said shelland attached to the base section thereof for heating the under surfaceof said strip, a resilient gasket adapted to seal the edges of saidshell at the juncture of the cover and base sections thereof, and meansfor evacuating said shell.

,2. Apparatus for heating a metal strip in vacuo comprising; a generallycylindrical closed-end shell, having a horizontal axis and beingsectioned on a longitudinal plane extending axially and inclinedupwardly and rearwardly at an angle of about 30 degrees to the verticalto form a cover section and a base section thereof, said cover sectionbeing hingedly attached to said base section at the juncture of the topedges of said base and cover sections, a pair of spaced apart spoolshorizontally and rotatably mounted in said shell and attached to thebase section thereof, means for rotating at least one of said spools, aguide roll mounted in said shell and rotatably attached to the basesection thereof, means mounted in said shell and attached to the coversection thereof for heating the upper surface of a metal strip disposedbetween and coiled on said spools, means mounted in said shell andattached to the base section thereof for heating the under surface ofsaid strip, a resilient gasket adapted to seal the edges of said shellat the juncture of the cover and base sections thereof, and means forevacuating said shell.

3. Apparatus for heating a metal strip in vacuo comprising; a generallycylindrical closed-end shell, having a horizontal axis and beingsectioned on a longitudinal plane extending axially and inclinedupwardly and rearwardly at an angle between 20 and 50 degrees to thevertical to form a cover section and a base section thereof, said coversection being hingedly attached to said base section at the juncture ofthe top edges of said baseand cover sections, a pair of spaced apartspools horizontally and rotatably mounted in said shell and attached tothe base section thereof, means for rotating at least one of saidspools, a cooling roll mounted in said shell rotatably attached to thecover section thereof and a cooling roll mounted in said shell rotatablyattached to the base section thereof, a guide roll mounted in said shelland rotatably attached to the base section thereof, means mounted insaid shell and attached to the cover section thereof for heating theupper surface of a metal strip disposed between and coiled on saidspools, means mounted in said shell and attached to the base sectionthereof for heating the under surface of said strip, a resilient gasketadapted to seal the edges of said shell at the juncture of the cover andbase sections thereof, and means for evacuating said shell,

4. Apparatus for heating a metal strip in vacuo comprising; a generallycylindrical closed-end shell, having a horizontal axis and beingsectioned on a longitudinal plane extending axially and inclinedupwardly and rearwardly at an angle between 20 and 50 degrees to thevertical to form a cover section and a base section thereof, said coversection being hingedly attached to said 6. base section at the junctureof the top edges of said base and cover sections, a pair of spaced apartspools horizontally and rotatably mounted in said shell and attached tothe base section thereof, means for rotating at least one of saidspools, a cooling roll mounted in said shell rotatably attached to thecover section thereof and a pair of cooling rolls mounted in said shelland rotatably attached to the base section thereof with the cooling rollattached to the cover section positioned laterally mid-way between thepair of cooling rolls attached to the base section and when the coversection is closed its lower edge will be lower than the upper edges ofthe cooling rolls attached to the base section, a guide roll mounted insaid shell and rotatably attached to the base section thereof, meansmounted in said shell and attached to the cover section thereof forheating the upper surface of a metal strip disposed between and coiledon said spools, means mounted in said shell and attached to the basesection thereof for heating the under surface of said strip, a resilientgasket adapted to seal the edges of said shell at the juncture of thecover and base sections thereof, and means for evacuating said shell.

5. Apparatus for heating a metal strip in vacuo comprising; a generallycylindrical closed-end shell, having a horizontal axis and beingsectioned on a longitudinal plane extending axially and inclinedupwardly and rearwardly at a angle between 20 and 50 degrees to thevertical to form a cover section .and a base section thereof, said coversection being hingedly attached to said base section at the juncture ofthe top edges of said base and cover sections, a pair of spacedapartspools horizontally and rotatably mounted in said shell andattached to the base section thereof, means for rotating at least one ofsaid spools, a cooling roll mounted in said shell rotatably attached tothe cover section thereof and a pair of cooling rolls mounted in saidshell and rotatably attached to the base section thereof with thecooling roll attached to the cover section positioned laterally mid-waybetween the pair of cooling rolls attached to the base section and whenthe cover section is closed its lower edge will be lower than the upperedges of the cooling rolls attached to the base section, a guide rollmounted in said shell and rotatably attached to the base sectionthereof, means mounted in said shell and attached to the cover sectionthereof for heating the upper surface of a metal strip disposed betweenand coiled on said spools, means mounted in said shell and attached tothe base section thereof for heating the under surface of said strip,the tops of said guide roll, said means for heating the underside ofsaid strip and said lower cooling rolls lying in the same generalhorizontal plane, a resilient gasket adapted to seal the edges of saidshell at the juncture of the cover and base sections thereof, and meansfor evacuating said shell.

References Cited in the file of this patent UNITED STATES PATENTS1,732,244 Salzman Oct. 22, 1929 2,203,241 Waldron June 4, 1940 2,812,270Alexander Nov. 5, 1957

1. APPARATUS FOR HEATING A METAL STRIP IN VACUO COMPRISING; A GENERALLYCYLINDRICAL CLOSED-END SHELL, HAVING A HORIZONTAL AXIS AND BEINGSECTIONED ON A LONGITUDINAL PLANE EXTENDING AXIALLY AND INCLUDEDUPWARDLY AND REARWARDLY AT AN ANGLE BETWEEN 20 AND 50 DEGREES TO THEVERTICAL TO FORM A COVER SECTION AND A BASE SECTION THEREOF, SAID COVERSECTION BEING HINGEDLY ATTACHED TO SAID BASE SECTION AT THE JUNCTURE OFTHE TOP EDGES OF SAID BASE AND COVER SECTIONS, A PAIR OF SPACED APARTSPOOLS HORIZONTALLY AND ROTATABLY MOUNTED IN SAID SHELL AND ATTACHED TOTHE BASE SECTION THEREOF, MEANS FOR ROTATING AT LEAST ONE OF SAIDSPOOLS, A GUIDE ROLL MOUNTED IN SAID SHELL AND ROTATABLY ATTACHED TO THEBASE SECTION THEREOF, MEANS MOUNTED IN SAID SHELL AND ATTACHED TO THECOVER SECTION THEREOF FOR HEATING THE UPPER SURFACE OF A METAL STRIPDISPOSED BETWEEN AND COILED ON SAID SPOOLS, MEANS MOUNTED IN SAID SHELLAND ATTACHED TO THE BASE SECTION THEREOF FOR HEATING THE UNDER SURFACEOF SAID STRIP, A RESILIENT GASKET ADAPTED TO SEAL THE EDGES OF SAIDSHELL AT THE JUNCTURE OF THE COVER AND BASE SECTIONS THEREOF, AND MEANSFOR EVACUATING SAID SHELL.